variable type conversion

This is a discussion on variable type conversion within the C++ Programming forums, part of the General Programming Boards category; Does anybody know of a complete (extensive) guide for converting various data types. Many times I get compilation errors because ...

  1. #1
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    variable type conversion

    Does anybody know of a complete (extensive) guide for converting various data types. Many times I get compilation errors because different functions use different types of variables, such as unsigned char, BYTE, const char etc. So I'm looking for a an all purpose conversion guide, BYTE to char, unsigned char to char*, etc, etc etc. Its often very frustrating not being able to use the data from different apis since I'm not able to convert between them. Thanks in advance.

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    Safe practice often results in there being no need to perform such conversions. Consider why you have compilation errors before trying to blindly cover them up. The errors are warning you that something untoward is going to happen.

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    I understand that it is often better to find the root of the problem in the functions that you program with, but the programs that I do are only for personal use. Basically to automate various tasks that I do on my computer, so it is often easier to do a quick fix rather than have it work flawlessly. Especially since these programs only have to work for me and not on any other system. So if anybody has anything that shows various conversions let me know.

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    Basically to automate various tasks that I do on my computer, so it is often easier to do a quick fix rather than have it work flawlessly.
    I would think that one would be more open to quality issues when they are the end user as well as the engineer.
    So if anybody has anything that shows various conversions let me know.
    It depends greatly on the types in question. If a conversion is possible then you wouldn't be getting errors. If you receive a warning then you can silence the warning with a cast though doing so can be unsafe. For some conversions, such as string to integer, a library function can possibly do what you want.

  5. #5
    Guest Sebastiani's Avatar
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    Type-checking is provided as a service, not a hindrance, to us programmers that helps us avoid many of the errors that can occur when casting from one type to another. Of course, if you're absolutely *sure*, and just need a 'quick' cast, you can use a template like this one:

    Code:
    template <class t1, class t2>
     t1 & cast(t1 & dst, const t2 & src)
    {
     dst = (t1)src;
     return dst;
    }
    Code:
    #include <cmath>
    #include <complex>
    bool flip(bool value)
    {
           return std::pow
        (
            std::complex<float>(std::exp(1.0)), 
            std::complex<float>(0, 1) * std::complex<float>(std::atan(1.0)*(1 << (value + 2)))
        ).real() < 0;
    }

  6. #6
    Confused Magos's Avatar
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    Guys guys, this is C++. Make use of the template casts:

    For normal casts:
    A = static_cast<TYPE>(B);

    For direct bitpattern casts:
    A = reinterpret_cast<TYPE>(B);

    For casting from a const type to a normal type:
    A = const_cast<TYPE>(B);

    There is also a dynamic_cast, but I'm not entirely sure what it does. I believe it's like the static_cast but does type checking dynamically (so it works better in inheritance situations?).
    Last edited by Magos; 02-25-2004 at 04:50 AM.
    MagosX.com

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  7. #7
    Disturbed Boy gustavosserra's Avatar
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    Originally posted by Magos
    There is also a dynamic_cast, but I'm not entirely sure what it does. I believe it's like the static_cast but does type checking dynamically (so it works better in inheritance situations?). [/B]
    Magos, I think that dynamic cast is suitable were, for example you have two classes from one, like this:

    Code:
    class Base{
       //code
    };
    
    class In_A : public Base{
       //code
    };
    
    class In_B : public Base{
    
    };
    At execution time, a pointer to Base could be pointing to In_A or In_B, depending on input from the user. So, there is no way to assure, at compiling time, when trying to dynamic cast from Base to In_B if the pointer does not point to In_A. Sorry for the bad english, it is just an ideia anyway.
    Nothing more to tell about me...
    Happy day =)

  8. #8
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    Lightbulb Typecasting

    As you have probably gathered from the responses, type conversion is called typecasting.

    Look-up typecase and cast.

    The simplest (and least-safe, I believe) way to cast, is to put the new type in parenthesis in front of the variable:

    Code:
    char c ;
    int i = 1 ;
    
    c = (char)i ;     //  Converts i to type char, then assigns value to c
    unsigned char to char*,
    That's a real error! The function needs a pointer to a c-style string, and you are trying to pass-in a single character.

    A couple of other topics to look-up (if you are not already familiar with them) are:
    function overloading
    templates

    Joining in the chorus: You should always try to avoid typecasting. It's a good way to make a compiler warning/error go away, and create a nasty hard-to-find run-time bug! You should almost never need typcasting for functions you've written yourself... if you've planned carefully. You might need it for library functions.

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